The present invention pertains to the manufacture of valves and like devices, and particularly to a process of efficiently producing valve stems surrounded by rubber or the like so as to form an assembly that is easily attachable to rubber tubes adapted for use in tires.
In order to provide complete background information so that the objectives and purposes of the present invention may be thoroughly appreciated, reference may be made to a number of U.S. Pat. Nos. 583,437; 1,931,649; 1,938,816; 2,014,129; 2,499,565; 2,600,942; 2,724,423; 3,474,498. In particular, U.S. Pat. No. 583,437 relates to a method of molding, around a valve stem, a rubber sleeve, the base of which is formed with depressions or corrugations; such construction is for the purpose of preventing shearing strain from being exerted on the base due to the normal creeping of the tire tube on the wheel rim with which the valve stem is associated. U.S. Pat. No. 1,938,816 discloses a general notion of roughening the surface of a sectional mold which is designed to vulcanize or otherwise unite a valve stem base member to a tire tube. However, the purpose of the method of this latter patent is to insure that the roughening provided in the resultant product spans the seam between the edges of the base member and the tire tube; accordingly, the roughening of the base member is produced on a surface not extensively in contact with the tube. As will be made clear hereinafter, the purposes and objects of the present invention differ substantially from the aforecited art.
It has long been known to fabricate valve stem assemblies in which processes a conventional valve stem is surrounded by a sleeve of rubber material which is so shaped or formed as to have a broad base or flange member suitable for attaching the entire assembly to a rubber tube. The attachment or joinder is generally accomplished by a vulcanization or similar step; however, in performing same it has been necessary, in order to insure proper bonding, to provide that the outer surface of the base or flange of the rubber sleeve be suitably roughened. The roughening is conventionally accomplished by abrading the aforenoted molded surface, generally by mounting the valve assemblies with respect to dials in a buffing machine which is indexed on successive wire wheel brushes.
It will be understood that the roughening or abrading process is a time-consuming operation; accordingly, it is a primary object of the present invention to eliminate this abrading or roughening step while enabling the same satisfactory bonding in the subsequent vulcanization procedure.
Another object is to reduce substantially the cost of the bonding process by completely eliminating the roughening step.
A primary feature of the present invention resides in the fulfillment of the above objects by providing that the mold plunger or similar portion of the mold apparatus be so configured that the outer surface of the base or flange will simulate the normally roughened surface. This is achieved by a configuration of fine cross-hatching or knurling, by which is meant that the surface of the mold portion preferably has a series of intersecting ridge lines with grooves defined therebetween, the particular pattern generally being diamond or V-shaped and with very close spacing between the ridge lines. The configuration for the mold portion is realized by well-known machining processes to produce the requisite pattern.
Considered in its method aspects, the present invention achieves, in a subsequent vulcanization step, effective bonding between the base or flange of a molded rubber valve device and a tire tube of rubber or the like, involving appropriate configuring or patterning of the surface of said base which contacts the tube surface, by the improvement which comprises simulating the required base surface normally resulting from abrasion by forming the surface of the contacting mold portion in a cross-hatched pattern.
The resulting product of the present invention is a valve or valve stem device which is surrounded by a rubber sleeve or the like having a base or flange member whose outer surface is configured as already described; that is, whose surface is cross-hatched due to contact with a cross-hatched mold portion.
Other and further objects, advantages and features of the present invention will be understood by reference to the following specification in conjunction with the annexed drawing, wherein like parts have been given like numbers.